Burner control apparatus and system



A. 1 JuDsoN 2,075,289

BURNER CONTROL APPARATUS AND SYSTEM Filed Deo. '7, 1952 4 sheets-sheet 1 March 30, 1937.

March 30,193.7. A. L. JUDSON' 2,675,289

BURNER CONTROL APPARATUS AND SYSTEM Filed Deo. '7, 1932 4 Sheets-Sheet 2 March 30, 1937. A, L. JUDSON 2,075,289l

BURNER CONTROL APPARATUS AND SYSTEM Filed Dec. 7, 1932 '4 sheets-sheet 5 March 3o, 1937. L- JUDSON 2,075,289

BURNER CONTROL APPARATUS AND SYSTEM Filed Deo. 7, 1932 4 Sheets-Sheet 4 10 146 Z3 Yf/-forL/v/ f j? 4 -l f2 ZZ 3 4,4 4,6

g2 d@ 173 Q jgrnggT-R ggg/T33 Moran ,0l/L Tllfffr-w) /9 v \TOBf .34 f *7 30 13 2 64 $7/ 49 Z5 o7 ma Patented 30, 1937 f UNITED STATES BURNER CONTROL APPARATUS SYSTEM AND Albert L. Judson, `Beloit, Wis., assignor to Minneapolis-Honeywell Regulator Co., Minneapolis, Minn., a corporation of Delaware Application December 7, 1932, Serial No. 646,080

19 Claims.

This invention relates to apparatus for automatically controlled systems, preferably automatically controlled heating systems, and it has reference to the construction, assembly, installation and circuit connections of such apparatus in systems for automatically controlling the operation of oil burners, and the like, for heating systems, v

The apparatus heretofore developed for controlling the operation of systems of the character referred to and for providing the essential protective features in such systems has included a lconsiderable number of separate devices requiring a great deal of skilled labor in installing the apparatus. Experience with different types of systems has shown that means must be provided for affording protection against numerous hazards and undesirable operating conditions, and the provision of such protective apparatus has led to Ya great complication of apparatus and connections in the systems now in use.

Accordingly, `the present invention provides for improved apparatus 'of unit assembly, which I preferably term a lockswitch, and which may include a magnetically operated switch controlling the operation of the burner motor, a thermally actuated lockout mechanism incorporating a manual reset which serves asa safety device when ignition does not properly take place at the burner, and a number of switches actuated by changes in stack. temperature and arranged to provide the desired sequence of operation of the oil burner itself or of other safety or operating controls. These switches may comprise a switch controlling the operation of the burner ignition and a pair of switches governing the functioning of the magnetically operated switch controlling the burner motor. Y

Broadly, an object of the inventionis to pro-v ber, or the operation of a burner motor, is controlled by a member which is moved from one position to another by the action of the magneticv vide a 'control systeml for heating apparatus in which the supply of fuel to a combustion cham ture, boiler or furnace temperature or boiler pressure.

A further object of the invention is the provision of an electrical control system for an electrically controlled-fuel supply device, the circuit towhich is controlled by a switch that is normally biased to open position and is moved to closed position by the inter-action of the magnetic fluxes produced by the concurrent energization of the primary and secondary coils of a step-down transformer and controlling the energization of the secondary coil in response to a heat condition which it is desired to control.

Another object of the invention is the moving of a fuel supply control switch to closed circuit position by the energization of an electro-magnetic coil when combustion is absent, and reducingl the energization of said coil upon the establishment of combustion, preferably by the insertion of a resistance in series circuit therewith upon operation of a thermal switch responsive to combustion temperature.

Another object of the invention is the provision of an automatic electrical control system for a fuel burner in which provision is made whereby the control. system supervises its own operation so that the supply of fuel is discontinued until manual intervention if the control system fails to operate properly.

Another object of the invention isto provide control apparatus for automatically controlled heating systems including fuel feeding means and actuating means therefor, in which the actuating means may be controlled by the current I'low in a control circuit and a transformer provided with a secondary coilin the control circuit and a primary coil in the main powery supply circuit so that the magnetic fluxes resulting from the energization of the transformer coils will-be instrumental in influencing a relay armature to control the fuel feeding actuating means.

A` still further object-of the invention is to provideV control apparatus of this type operating on the transformer relay principle inwhich cer-y tain control devices responsive to combustion con. ditionsestablished by the burner are adapted to reduce the current flowthrough the secondary coil and thereby decrease the effective magnetic pull of the transformer core sufficiently to hold the relay armature in actuated position but to release the amature upon current failure 'or serious reductionof current in the line and prevent subsequent actuation of the armature for a timed period, after which the larger current flow 'through the secondary is restored.

how to practice 'and construct the invention, I shallnow 4describe a preferred embodiment thereof in connectionf with the accompanying drawings, in which:

Figure 1 is a front elevational view of anassembly of control apparatus designed in accordance with the present invention; y

Fig. 2 is a perspective view ofthe relay armature carrying thev burner motor switch, as shown in Fig. 1:

Fig. 3 is a view similar to Fig. 1, with certain parts omitted;

Fig. 4 is a vertical sectional v`view taken on a line 4-4 of Fig. 1; i

Fig. 5 is a fragmentary detailed view of a portionof the control apparatus and circuit connections carried atthe'rear -of the base;

Fig. 6 is a schematic representation of animproved system of circuit connectionsd designed for use inconnection with the apparatus disclosed in the previous figures;

Fig. 7 is a schematic representation of a modiiied system of circuit connections designed for the same use; and

Fig.'8 is a detail view of the carriage and switch of the thermallyactuated lockout mechanism.

Referring first to Figs. 1 to 5, inclusive, of the drawings, the apparatus disclosed comprises a 30 sheet'metal member 5 forming a base plate for furnishedto complete the enclosureoLthe apparatus. In Fig. 4 a cover 1 is arra': j to extend over the apparatus on baseplate 5 an, .be secured bers 9 Jxed to this baseplate. Terminal mem'- bers I0, II, I2, I3, I4, I5, I5, I1, I5 and I9 are carriedby suitable supportingimembers 20 and 2| of insulation material at the front of the base 5, and, with the exception of terminal I2, which is a permanent connection, are provided with suitable screws for the attachment oi circuit connections thereto. Terminals I0 and II are adapted to have a supply circuit connected thereto. Two electrodes of a mercury contactor 22 are connected between the terminals I5 and I2 by means of flexible connecting leads 23 and 24 and the terminals and I2 are directly connected to the primary coil 25 of a transformer 26 by conductors 21 and 34 located at the rear of the insulation plate or terminal ,board 20. The terminals I3 and I4 are adapted to have connected thereto conductors extending to the mo- `tor or other actuating mechanism of an oil burner or similar device. The terminal I4 is connected to line terminal II by a conductor I4' located at the rear of the terminal board 25.

The electrodes of a mercury contactor 28 are connected by flexible conducting leads 29 and 35 to terminals I3 and I5. The electrodes of a. mercury contactor 3| are connected between the terminals I2 and I3 by exible conducting leads 32 and 33. Thus the terminal' I3 is connected to the terminal I5 by the contactors 22 and 3|A connected in series, while terminal I4 and the terminal I5 are adapted vto have connected thereto conductors extending to the ignition'device of the burner system. With this arrangement, it will be seen that the ignition circuit is connected to the supply conductors extending to the terminals I0 and Il through the three switches 22, 3| an I theretoby'screws 8 cooperating with angle mem- Y 28 connected in series.

The conductor 21 and the conductor 34 are disposed' on the back of theterminal board 20, and

extend from lineV terminal I I and the terminal I2 to the primary winding 25 v4of transformer 26 that is utilized to supply current at a reduced'voltage 'to certain of the control' apparatus to be described. The frame of this transformer is preferably secured directly to the base plate 5 by screws 35, the base plate 5 being suitably cut away as indicated at 31 (Fig. 5) to provide room for the primary winding 25 of the transformer. 'Ihe base plate 5 is also cut away at 38 to provide room for the secondary winding 39 of the transformer, said `cut-away portions 31 and 38 being clearly shown in Fig. 5. One terminalof the secondary winding 39 is connected through a conducting lead 40 to the terminal` I5; this conduct- ,l

ing lead extending upwardly from the secondary winding at the baci; of base plate 5, and extending through an aperture 4I to connect to this connected through a flexible lead to a terminal "connecting by a flexible lead 48 to a terminal49 of an electrical heating element 50.

' The other V'telirlinal-BI' vof the heating element 50 is connected through a flexible lead 52, disposed on the back of base plate'5, to the binding postfvI8, to which may be connected one ofthe termi'- nals of a limit control 53 hereinaftento be de-v scribed. The flexible lead 52 extends through an aperture 55 in base plate 5,y as shown in Figs. 1

and 3, to connect with binding post I5. I

:terminal screw, 55 is located upon base plate 5 adjacent to the terminal screw43 and is ,con-

nected throughwa exible lead 51'to one roigtwo I electrode of contactor 58 is connected through a flexible lead 59 to the terminal 41.

' As illustrated in Fig. 5, terminals 41 and 5I extend through the base plate 5, and an insulation strip is secured in position by rivets 52 extending through base plate 5. Terminals 43 and 55 likewiseextend through the base plate 5 and.

insulation mounting and secure in position an insulation plate 63, comprising, together with a winding 54, a hold resistor connected between the terminals 43 and 55, this being clearly shown in Fig. 5.

An auxiliary secondary winding, together with electrodes ofa mercury'contactor 58. 'The other certain of the controls described, constitutes an ultimate safety secondary circuit having a flexible lead 55 connecting to the terminal 55 and a ilexible lead 55 connecting to the binding'post I9, to which is connected one of -thecontacts of the limit control 53, both flexible leads 55 and 55 being disposed at the rear of the base plate 5.,

The contactor 3| controlling the circuit of the motor or other actuating means for the burner is mounted for pivotal movement upon an arm 61, which arm is connected by a 'screw 55 to a relay armature designated broadly as 59. The relay armature 69 is mounted for pivotal movement at 1li, shown in Fig.3, adjacent to the core 1I of transformer 26. Core 1I may be of any suitable construction, which as shown in the drawings,

comprises the plurality of laminated bars 12 ,se-

the primary coil 25 and an ultimate safety secondary coil |12, (shown in Figure 4) to be hereinafter described, to be wrapped thereabout along one leg and the secondary coil 39 to be wrapped about one of the shorter legs and at right angles to` primary coil 25 and the said'secondary coll I 12.

The laminated bars 12 of core 1| are secured together to form a transformer frame that is secured to base plate 5 by screws 35. -Rivets 13 may also be used at various points along the core to maintain bars 12 as a rigid unit. The pivotal movement of relay armature 69 at 10 tilts contactor 3| either to open or closed position. A weight 14 may be secured by a screw 15 to the free end of the bar 61, and the relay armature 69 allowed to tilt counterclockwise by gravity about the point 10 when the transformer is deenergized by a failure or serious reduction in the line voltage that would'prevent proper functioning vof the burner and its control parts. Shading pieces 16 are provided at the free end of the relay armature 69 to eliminate the vibration or humming of the armature which would normally occur from the use of alternating current.

A bracket 11 is secured by the screw 68 to the armature 89 with its arm 18 acting as a stop for the armature by engaging any suitable part, say the upper edge of the upper leg of the' core 1|, to limit the movement of the armature when tilted counterclockwise by the gravity action of weight 19.

The detail construction of the transformer relay and its armature may be changed to meet particular requirements. The invention is mainly directed to utilizing the flow of current through a transformer relay to actuate the switch 3| coni trolling the burner motor or other control device.

the drawings have been generallydescribed above,

and the detail of construction and assembly of these elemnts will now be described. The mercury contactors 28 and 45 are carried by clips or holders and 8|, respectively, (see Fig. 4) and these clips are secured to downwardly and upwardly extending arms of a member 82 that is centrally perforated to permit the extension of an actuating rod 83 therethrough. The central portion of the member 82 is cup-shaped to receive the forward extremity of a compressionspring 84, the rear extremity of which is received by a cup member 85. 'Ihe periphery of the cup member85 is forwardly presented or anged and the member itself is fixed upon one end of a sleeve 86 loosely mounted upon rod 83. Sleeve 86 extends through the aperture in the cup-shaped portion of member 82, and a frlctional washer 81 is preferably provided between the forward extremity of the spring 84 and the inner surface of this cup-shaped portion of member 82, while a similar washer is preferably disposed between the rear extremity of spring 84 and the cup-member 85. A washer 86a is secured to the front end of sleeve 86 and forward of the member 82 whereby the washed 86a., sleeve 86 and cup member 85 form a unitary structure and the member 82 is spring pressed against washer 86a by means of the coiled spring 84 which is confined between member 82 and cup member 85. As the result, the member 82 normally rotates with the sleeve 86 but may be restrained from so moving holder 9 I.

spring 84 pressing the member 82 against the washer 86a. Thus, a frictional slip connection is provided between the rod 83 and the member 82 to which the mercury contactors 28 and 45 are secured.

A similar arrangement is provided between the rod 83 and a member 90, to which the mercury contacter 58 is secured by means of a .clip or 91 which loosely engages the rod 83, a cup member 92 which is secured to one end of sleeve 91 This arrangement comprises a sleeve.,

and a washer 91a which is secured to the other whereby member 90 is pressed against washerv 91a. are placed between the ends of spring 93 and 'cup member 92 and the cupped portion of member 90.

By this arrangement, member 90 normally rotates with sleeve 91 but may remain stationary if constrained against movement with sleeve 91 since thespring 93 pressing member 92 against washer 91a forms a slip `frictional connection therebetween.

Acollar 96 is secured to rod 8. Sleeves 91. and 88 are next loosely placed on the rod 83 and a nut 98 is threaded on the extremity of rod 83 and turned down tightly against sleeve 86 whereby sleeves 86 and 91 are held between collar 96 and nut 98 and must therefore move in conformity with the movements of rod 83.

A collar 99 is adjustably secured by a. screw |00 to rod 83. A sleeve member |0| extends rearwardly from a heat insulating shield plate |02.mounted at the rear of face/plate 5 by a plurality of screws |03 threading into mounting posts |04'rigidly Xed to the rear face of mount;- ing' plate 5. Dgetachable means, such as bolts |06, may be used to secure sleeve |01 in position. The rear extremity of sleeve |0| receives the foremost portion of a coiled bimetalllc or other suitable thermostatic element |01, and the end vof the element |01 is secured to the sleeve Mil by means of a screw |08, passing through an angle guide |09, lnteriorly disposed insleeve |0| and apertured at' ||0 to allow rod 83 to pass therethrough. From this point the thermostatic element |01 extends rearwardly for a substantial distance whereby this exposed portion of the ele- Preferably, frlctional washers 94 and 95 i ment may be disposed within a stack or flue of the furnace to render said element responsive to conditions of combustion in the furnace.

The rod 83 extends rearwardly through the entire length of sleeve |0'| and the thermostatic Y element |01-is in axial relation to these members and is angularly bent at its rearmost extremity. This angularly bent portion of the element |01 is secured to the extreme outer end of the rod 83 by a screw and a nut ||2 for rmly Ssecuring the rod 83 to the end of the thermostatic element |01.

It will' be understood that when the thermostatic element 01 is subjected to varying temperatures due to different conditions of combustion in the furnace or combustion chamber tor be controlled by the system, the 'rearward ex- Y tremity of this thermostatic element is rotated by reason of the expansion and contraction of its coils. This rotation is transmitted directly to rodl 83 and thus to a limited extent to ,members 82 and 90 which support the mercury contactors or switches 28, 45 and 58. 'Ille limitation of movementof the members 82 and 80 is permitted by reason of the frictional slip connections beL tween these members and the rod 83 as above devscribed.. 'riicsc limitations are dennitciy fixed by stop members H3, H4, H and H8, which are adapted to be engaged by members 82 and 88 in different positions thereof. 'I'he stop members q H3, I I5 and H5 are adjustable in slots H1 and the movementA of member 98 carrying the 'conmit continued rotational movement of rod 88 by the thermostatic element |81. Stp member I|5 is adjustable in slot ||8 likewise to predetermine tactorl 58 before its frictional slip connection be comes effective to allow continued movement of rod 83 by the thermostatic element '|81.

It will be seen that stop members H3 and II4 adjustably limit the extreme counterclockwise position of members 82 and 88, respectively, and

. the stop members H6 and ||5 adjustably limit the clockwise movement of members 82 and 98, respectively. The thermostatic element |81 is so arranged that the rod 83 is rotated in arjclockwisedirection, as viewed in Fig. 1, as this ther.

mostatic element is heated. Cooling of the mernber |81 thus obviously eects counterclockwise rotation of the rod 83, as viewed in the same figure. While the member |81 is relatively cool, therefore, which condition corresponds to the absence of combustion in the furnace or combustion chamber that is to be controlled, the members 82 and 98 are in their extreme counterclockwise positions as shown in Figs. 1 and. 3. When these members occupy such positions the'container for each of the mercury contactors 28, and 58 is tilted downwardly'to the left as shown.

. Each of the contactors comprises a single pair of electrodes, the electrodes in the contactors 28 and 45 being located in the left-hand extremities of the respective containers so that both of these switches are closed inthis position. The electrodes of contactar 58 vare located in the righthand extremity oi.' the container so that this switchA is opened in its lefthand position, as

shown in Figs. 1 and 3.

The temperature of the thermostatic element |81 is raised due to the establishment of combustion in the furnace or combustion chamber to be controlled. The rod 83 is gradually rotated in clockwise direction, asf viewed in Fig. 1. After a predetermined extent of such rotation, the

. switch 58 is tilted to such an extent that the body of mercury therein is caused to flow from the left-hand extremity of its container to the right-hand extremity thereof, thus closing the' lcircuit connection'between conductors 81 and 58. This action precedes that o! the switches 28 and 45, because the angle of inclination ofthe container for the switch 58, in a direction downward and to the left, as viewed in Fig. 1, is less in the extreme counterclockwise position than is the angle oi inclination of the switches 28 and 45` After the switch 58 is moved to closed circuit position, the member 88 which supports said switch engages the adjustable stop H5 whereby further movement of the switchl 58 andthe member 98 is prevented..

As the rotation oi rod 83 continues, the circuit, between the two electrodes of switch 45 is next' opened, which electrodes are connected across a circuit comprising the resistor 64 and the two electrodes at the right-hand extremity of switch 58, to which latter electrodes the conductors 51 and 58 are respectively connected. The opening of the switch 45 is brought about subsequently to the closing of the switch 58 by reason of the curved or humped formation of the container for the switch 45 and `for the further reason that it is inclined further to the left.

As the rotation of the rod 83 continues further, and after switch 58 has closed and switch 45 has opened, the switch 28 is tilted to "such an extent that the body of mercury within its container is moved from the left-hand extremity. of said container to the. right-hand extremity to interrupt the circuit connection between the conductors 29 and 38, which are respectively connected to the two electrodes in the left-.hand extremity of the container forv this switch 28.

The opening of the circuit between the electrodes l of switch 28 interrupts the ignition circuit of the burner control system, as will hereinafter appear in connection with the 4description of the en-A tire system of circuit connections. f

K As the rotation ofthe rod 83 continues further, -and after the switch 88 has closed, the switch 45 has opened zand the. switch 28 has opened `then the movement of -member 82, 'which supports switches 45 and28, is arrested by engagement of the uppersportionot this member with the stop I I6. When the two members 88 and 82 have been thus actuated in sequence to their extreme clockwise positions, as determined by the adjustable stops I I5 and H8, respectively, further movement of the thermostatic element |81 in response to a tuation of the members 82 and 98 toward their original positions, as shown in Figs. 1 and 3, is initiated. The switch 58 first opens and the member 98, in moving through a relatively short arc, engages the stop pin H4. Next, the switch 28 moves to. closed circuit position land thereafter the switch 45, after an appreciable interval oi' time, as measured from the opening of the switch 58, moves to closed circuit position and the member 82 engages the adjustable stop pin I3. 'Ihe arc of movement allowed to the switches `45 and 28 as measured by the distance between the adjustable stop pins H5 and H3, is substantially greater than the arc of movement allowed to the switch 58 which is 4measured by the iixed stop pin I4 andthe adjustable stop pin I|5. The hump formed in the container oi the switch 45 further serves to delay the closing cf the circuit through this switch' csihc switch is moved in a counterclockwise direction upon the cooling of the thermostatic element |81. The reasons for providing hthe aforementioned sequence of operation of the switches 58, 28, and

45 will hereinafter appear.

The container tube of switch 22 is embraced by va clip or holder I28that is secured to a pivotally mounted member I2I. (See Figs. 3 and 8.) The latter member is journalled upon a pin or rod |22 carried by and extending forwardly ofbase plate 5. A pinv 23 is used to permit member |2I to be easily removed from shown in Figs. 1 and 3.

pin |22. The member |2| has horizontally extending apertured lugs |24 and |25. The aperture in lug |25 is screw-threaded to receive a threaded portion of a vertically extending pin |26, this pin also passing through the aperture in lug |24. A collar |21 is iixed to pin |26 to act as an abutment for one extremity of a spring |28, the opposite extremity of spring |28 abutting against lug |24. A slotted head |29 at the lower end of pin |26 allows vertical adjustment of pin |26. Arm |30 is'extended to carry clip |20 embracing the container tube ofA switch 22 a distance beyond the pivotal mounting pin |22 suillcient to allow the weight of the container to cause contactor 22 normally to tilt by gravity clockwise. The two electrodes of switch'22 being located near the left-hand end of the container, it will be seen that this switch will be closed when it occupies the normal position The gravity action tending to tilt switch 22 clockwise or to the right and to cause the body of mercury in the container of this switch to move to the right and open the circuit at the electrodes, is nor-v mally restrained by a forwardly extending leg |32 of a bimetallic element |33.

Upon a predetermined upward deflection of the bimetallic element |33, however, the extremity |32 moves out ofY the path of the upper end of pin |26, whereupon the action of gravity upon switch 22 causes this switch to move pivotally about the rod or pin |22 in a clockwise direction, as viewed in Figs. 1 and 3. Such movement causes the switch 22 to be tilted downwardly to the right, whereby the mercury within the container is moved to the right-hand extremity to open the circuit through the two electrodes of this switch. The upward deection of the bimetallic member |33 is eiected by an increase in the temperature thereof in response to energization of the electrical heating element 50 in v the manner which will appear hereinafter. For

the purpose of rendering this part of the apparatus independent of ambient temperatures', the bimetallic element |33 is supported by means of screws |35 forming, with a spacing collar, |36 and nuts |31, a connection with the left-hand extremity of a, second bimetallic element |38. (See Fig. 3.) The latter bimetallic element is rigidly supported upon a forwardly extending portion |39 of bracket member |40. The bimetallic member |38 operates in a manner opposite to that in which the member |33 operates, that is, the right-hand extremity of the member |38 is deflected downwardly in response to a rise in temperature.

Thertwo` bimetallic elements 33 and |38 are so proportioned that the deiiections effected by changes in ambient temperatures will exactly balance one another and will have no eect whatever upon the position of the left-hand extremity ofthe bimetallic element |33. The heating element 50 is disposed to eifect the bimetallic member |33 without aecting the member |38. Heating element 5l il carried upon brackets |'4| and |42,-ri'feted at I2 and 49, respectively to the insulation plate 06 secured at the rear face of base plate 5. (See Fig. 5.)

The portion 'of the baseplate 5 cutaway as indicated at 31to provide room for the primary winding 25 is slightly enlarged, as indicated at |43, to allow for the connection of brackets |4| and |42 to the insulation plate 60. A horizontal heat insulating plate |4415 carried between the brekets m and |42 and directly be1ow heating element 50.

Referring now to conductors |46 and |41 are shown, it being understood that these conductors will be'respectivelyA connected to the line terminals I0 and carried by the terminal board 20 of the control apparatus, as heretofore described in connection with Fig. l. A motor or other burner actuating apparatus |48 is connected in the circuit by means of conductors |49 and |50, which will be respectively connected to the motor terminals I3 and I4, as shown in Fig. 1. Connections to an ignition device |5| are made through a conductor |52 and |52 connected to terminals |5 and |4, respectively.

'I'he terminals I6, l1 and |8 are located in the control circuit between the conductors and 52 to facilitate the connection of a room thermostatic switch |55 and the switch 53 of the boiler control or similar device in the circuit. In Fig. 6 of the drawings, the room thermostatic switch is diagrammatically shown and the switch of the boiler control or similar device is diagrammatically shown, these two switches being connected in series relation to each other by the conductors |56 and |51. The other terminal of the room thermostatic switch |55'is connected to the conductor 40 by means of a conductor |58, and the other terminal of the switch of the boiler control or similar device is'connected to the conductor 52 by means of the conductor |59.

The`remaining connections of the control circuit, as described in connection with Fig. 1, comprises a series circuit extendingv from the conductor 52 through the lockout resistor 50 and conductor 48, the terminal 41, conductorl 46 through the recycling or pull switch 45, the conductor 44, terminal 43 and the conductor 42 to the opposite transformer secondary terminal. The operation of the control system connected according to Fig. 6 is normally controlled by the room thermostatic switch |55, which is arranged in any well known manner to be responsive to the temperature of the room to be heated.

Operation.

Referring te Fig. s, it w111 be noted that the primary winding 25 of thetransformer 26 is normally constantly energized by the following circuit: Current ows through the conductor |46, terminal I0, conductor 23, lockout switch 22, conductor 24, terminal l2, conductor 34, the primary winding 25 of the transformer 26, conductor 21, terminal il, and line conductor |41. It is customary to supply with controls for oil burner motors a low water cut-off device which is shown diagrammatically at |13 and, inthe event that such a safety device is applied, then the same may be connected in advance of the binding post |0. This energization of primary winding 25 establishes a magnetic ux which travels unre-A as follows: Secondary '39, conductor 42, terminal 43, conductor 44, switch 45, conductor 46,

terminal `41, conductor 48, lockout resistor 50, conductor 52, terminal I8, conductor |58, electrodes |6| and |60 of the limit control switch 63,

Fig. 6, two currentsupply 4 col conductor |51, terminal |1, conductor |58, room thermostat |55, conductor |58, terminal |8, and

conductor 48 to the other side of secondary' 39. Completion of this circuit through relay secondv, ary 39 establishes a magnetic flux which opposes the magnetic ux set up by primary winding 25 with the result that some ci this ilux from the primary winding 25 must travel through armature 88. This diverting of the magnetic flux mature 89 and moves it into engagement with the core 1I whereby motor switch- 3| is tilted to its closed circuit position to establish a'motor energizing circuit which is as iollows: Line |48, l5 terminal I8, conductor 23, lockout switch 22, .con-

ductor 24, terminal I2, conductor` 32, motor switch 3|, conductor 33, terminal I3, conductor |48, motor |48, conductor |58, terminal I4, conductor I4', terminal II, and line |41.

An oil valve |88 may beconnected in parallel with motor |48 if it is desired to use an oil valve in the control system.

- Closure of motor switch 3| likewise establishes an ignition circuit which starts at the terminal switch 28, conductor 38, terminal I5, conductor |52, ignition device |5I, and conductor |52' to extent atthe end of a predetermined time, that the end |32 thereof will move out of engagement with the end of pin |28 thereby allowing lockout switch 22 to. tilt in a clockwise direction about the pivot |22 under the iniluence of gravity to open the circuit through lockout switch 22. It this happens the energizing circuits for the motorv |48, oil valve |88, ignition means I5I, and the primary winding 25 oi transformer 2 8 will all be interrupted and the controlsystem will be rendered inoperative until lockout switch 22 is reclosed manually by operation of -a manual 'reset comprising a button |85.

The opening of switch'22 in this manner interrupts the control circuit and terminates the operation ofthe heating system. Consequently, when the lockout switch 22 is open, current can no longer iiow to any part of the system, and in order to re-establish any operation in the system, it is necessary to reset'the lockout switch 22, say, by means 'of a manual reset comprising a button |85. reset without removing the cover 1 of the casin and is constructed so that it cannot be operated except by being manually, turned. The button |85 extends upwardly through lower flange 8 of base plate 5, and the base plate 5 is cut away at '|88, with the cut-away portion struck downat .|81 to form a bearing for the pin I88.to which this button is attached. An actuatingpin |89, fixed to pin I88,.extends horizontally forward through the cut-away opening |88 to engage the head |29 on the lower end of 'pin |28. Themanual turning of `button |85 clockwise or to the right swings operating pin |88 against this head |28, whereby to swing the pivotally mounted member I 2| upwardly about pivot |22 and tilt the lockout switch |22 to the left to close the circuit at its electrodes. Y

If the trouble causing the failure of combustion 75 establishment has been remedied, the stack therthrough armature 89 attracts the free end of ar-` I3 and iiows through conductor 29, ignition 58 will heat bimetallic element |33 to such an The button |85 may be manually mostatic element |81 will respond to the rise in temperature in the stack, and cause rod 83 Vto rotate and close the hold switch 58 and open the pull switch 45, whereafter the ignition switch 28 the stack will remain cold and the thermostatic.

element |81 vwill not operate. The current will continue to iiow through the heat coil 5'8, to eil'ect another lockout operation of the switch 22. It

will be promptly determined,v therefore, whether the trouble causing rected.

Assuming that the fuel supplied by motor |48 is properly ignited by ignition means v-I5|, thermostatic element |81 will begin to heat and, as previouslyv described, will rst move switch 58 to circuit closed'position. vMovement of switch 58 to closed position establishes a circuit from terminal 43 through hold resistor 84, terminal 55, conductor 51, switch 58, and conductor 59 to terminal 41. It will be noted that this circuit through hold resistor 84 is shunted' by the circuit through switch 45 previously described.

Further heating of thermostatic element |81 will thereafter move switch 45 to open circuit position thereby removing the shunt around hold resistor 84 and switch 58 whereupon the circuit through relay secondary 38 will be as follows: Conductor 42, terminal 43, hold resistor 84, terthe lockout has been corminal 58, conductor 51, switch 58, conductor 58,

conductor 48 to the other side of relay secondary 39. It will be noted that hold resistor 84 is now in series circuit relationship with lockout resistor 58. This yreduces the current iiow through locklout resistor 58 to such .an extentwthat the heat L generated thereby is insuilicient to move the end l|32 of bimetallic element |33 out of engagement with` pin |28; In other words, insertion oi' hold resistor 84 in series with lockout resistor 58 operatively de-energizeslockout resistor 58 and consequently preventsthe lockout switch 22 from moving to open circuit position.l

4Continued heating of thermostatic element ythermostat |55 opens the circuit through -relay secondary 39. `^Of course, if the boiler temperature or pressure should become excessive, limit control switch 53 will be operated to move its mercury from its bridging relationship with terminals |88 and I 8|. This action likewise would open the circuit through relay secondary 38. If the water in the boiler should become too low,

the low water cut-oil' switch |13 would open the main line circuit to conductor |48 and discontinue operation of motor |48.

Ii there should be a flame failure-that is, if

the flame should become extinguished after having been initially successfully established-thermostatic element |81 will begin to cooland immediatelymove switch, 58 to open circuit position thereby interrupting the circuit through and the lockout resistor or heat coil 50.

- extending through the aperture 55 in the base relay secondary 39. Whenever the circuit through relay secondary 39 is interrupted, the magnetic flux set up by primary winding 25 will no longer be diverted through armature.

69, and the weight 14 wiil'tilt amature 69 in a counterclockwise direction to open motor switch 3|. Opening of motor switch 3| discontinues the supply of fuel to the combustion chamber. Continued cooling of thermal element|01 causes member' 90 to engage stationary stop 'H4 and thereafter closes ignition switch 28. Closure of ignition switch 28 will not re-energize ignition means |5| since motor switch 3| is still open. Further cooling of thermal element 01 will, after a time interval measured from the opening of switch 58, close switch 45 whereupon the circuit through relay secondary 39 will be again completed in the manner hereinbeforeV mentioned. 'I'he system will therefore again attempt to establish combustion in the usual manner. The time interval between the opening of switch 58 and the re-closing of switch 45 provides a standby period during which any hot oil vaporsA that may be present in the combustion chamber willbe dissipated so as to eliminate the possibility of an explosion when the ignition is re-established.

If there should be a momentary failure in the supply of electrical power while the system is operating to supply heat, all of the circuits will be interrupted and the motor switch 3| will return to open circuit. position. The thermostatic element |01 will begin to cool but if the supply of power is resumed before switch 58 has been moved to open circuit position, the series circuit through relay secondary 39, hold resistor 64, and lockout resistor 50 will allow such a-small flow of current through the relay secondary 39 that the flux diverted through amature 69 will be insuicient to move the armature 69 in a clockwise direction to close the circuit through motor switch 3|'. Therefore, the system will remain inoperative until switch 45 is closedfafter a time interval as a result of substantial cooling of thermostatic element |01, in a manner similar to that hereinbefore pointed out in respect to flame failure.

Ultimate safety The control system that constitutes the present invention provides l means by which faulty operation of the control system itself is checked.

A safety. circuit, which may be termed herein as an ultimate safety circuit, is provided to protect the system against the failure of the control apparatus itself to function properly. This ulti# mate safety circuit includes, as shown in Fig. 6, a third electrode of the limit control 53, an ultimate safety secondary |12, the hold switch 58, 'I'he third electrode |10 connects by means of a ilexible conductor |1| to the terminal i9, and this terminal I9 connects to the ultimate safety secondary |12 by means of a ilexible conductor 56 plate5, and connecting to` this secondary coil |12 at the back` of the base plate 5. y

With the controly system operating normally, the room thermostat .|55 may open the circuit through relay secondary 39 as a result of rise in room temperature', but the armature v|59 may fail to move the motor switch y3l to open circuit position. Also the room thermostat |55 may fail to open the circuit through relay secondary 39 because of faulty contact operation within the room thermostat |55. Under-either of these conditions the boiler temperature or pressure will become `excessive'so as to move switch 53 toa position in which the mercuryconta'nedin switch 53 will bridge electrodes |6| andi- |10. Bridging of electrodes IGI and |10 of switch 53 will establish the following circuit: Ultimate safety secondary 12, terminal 56, conductorv 51, switch 58, conductor 59, terminal B1, conductor 48, lockout resistor 50, conductor 52, terminal I8, conductor |59, electrodes |6| and |10, switch 53, conductor |1|, terminal I9, and conductor 66 to the other side of ultimate safetysecondary |12. out. resistor 58 which, in turn, will heat bimetallic element |33 to cause the end |32 thereof to move within a predetermined time out of engagement with pin |25 thereby allowing lockout switch 22 to move to open circuit position under the inuence of gravity. The movement of lockout switch 22 to open circuit position will render the entire control system inoperative until manually reset, as hereinbefore described. This same operation will result even though some of the mercury in limit switch V.53 continues to bridge electrodes |60 and |6| while another portion of the mercury bridges electrodes |6| and |10. By this arrangement it will be seen that this control system supervises its own correct operation.

The modified system of circuit connections shown in Fig. 7 is designed to provide the same operating and protective features that are obtained with the system illustrated in Fig. 6, but certain minor changes in the circuit connections of the ultimate safety .circuit are shown to illustrate the fact that this ultimate safety circuit is not limited to the use of a separate ultimate safety secondary coil |12 as shown in Fig. 6. The relay secondary coil 39 may be employed in the ultione of the electrodes of one pair arranged also to complete the circuit with one of the electrodes of the other pair.

Electrodes |80 and |8| complete the circuit during initial operation and before the stack thermostatic element |01 has responded to the rise in temperature in the stack Electrodes |82 and |83 complete the circuit of the ultimate-'safety circuit to operatively de- 'I'his circuit will operatively energize lock energize the transformer' relay and thereby allov.1 v

Vthe motor switch 3| to open when either the room thermostat or the limit control |18 opens. not open the circuit of the motor |48 when either the room thermostat |55 or the limit control |18 opens; the ultimate safety resistor |16 then funcy tions as a heater for the bimetallic element |33 of the thermally operated lockout mechanism, in. lieu of the lockout resistor or heater 50, to-

effect a permanent lockout of the apparatus by 4 opening the'lockout switch 22.

It will be understood that the ultimate safety resistor |18 may be suitably located, as is the heater 50, in thermal relation to bimetallic elelment |33, to cause warping of the latter and a consequent releasing of pin |25 to tilt thelockout switch 22 to open position when the cury rent flows through the ultimate safety resistor |16 for a predetermined time interval. When combustion is established and the stack thermostatic element |01 hasv responded to the rise in temperature in the stackto rotate rod 83 If the motor switch 3| should stick, and

clockwise, the hold tube |11 is tilted to the right `tocause the mercury to bridge electrodes |8|, |82, |83, and thereafter the pull switch 45 is opened. The circuit thus completed through the electrodes |8| and |83 and the hold resistor 84, will reduce the quantity of current owing through the secondary coil 38. This reduced current flow in the secondary coil 38 will, in turn, reduce the effective magnetic force holdlng the relay armature 88 insuch position as to hold the motor switch 3| closed, but this reduced magnetic force still continues to hold the motor switch 3| in closed position. l Considering now the condition yfollowing clos- 15 ing of the room thermostat |55, the current will flow from secondary 38, through wire |84, limit control |18, wire |85, room thermostat |55, wire |86, electrodes |8|-and '|88 of hold tube |11, wire |81, pull tube 45, lockout resistor 58, wire |88, and back .to the secondary coil 38. In the samemanneras previously described in connection vwith .the showing of Figs. 1 to 6, inclusive, the flow of current in the secondary coil 39 causes the magnetic force to actuate the relay amature 88 and close the motor switch 3|.

The ignition will be energized.

If combustion is not established in the furnace or combustion chamber within a suitable interval of time after the closing of 'the motor circuit, the lockout switch 22 will be opened at the end of such interval by reason of the fact that the thermcstatic element |81 remains cold in the stack and does not rotate rod 83 and tilt hold switch 11 and, thereafter open the pull switch 45 to deenergize the lockout resistor 58. Upon failure of the hold switch |11 to open the circuit 'described at electrodes |88 and |8I `and the pull switch 45 to open, current flowing' through the heating resistor 58 for a predetermined period will cause the bimetallic element |33 to warp.

The warping of the bimetallic element |33 raises its arm or. leg |32 out of the path of pin |26 and theraction of ygravity causes switch 22 to tilt clockwise about .its pivot |22 for the purpose of breaking the circuit between the'electrodes of this switch, the primary circuit being thereby opened as shown in Fig. 7.

' In order to carry out the safety lockout feature requiring manual resetting of the apparatus if switch 22 isopened by the action of the thermally operated element |33, button |85 is provided, but it will be understood that broadly, in connection v with both variant embodiments of the invention herein shown and described, the manual reset- 85- ting is preferable but not essential to the novlelty of-theother features described?.

If combustionl is established, the hold switch |11 will establish av holding circuit for the secondary coil 38 in which the current will flow from 80 the secondary coil 38, through wire |84, limit control |18, wire |85, thermostat |55, wire |88,

electrodes |8| and |83 of hold tube |11, wire |88,

The hold resistor 84 will reduce the flow of' the armature 68 until the power has been restored and/or the pull tube closes, as described in ,connection with Fig. 6.

When the room thermostat |55 issatised or the boiler pressure or temperature becomes exnetic force on armature 88 to such an extent 1 that the motor switch 3| should move to open circuit position. If motor switch 3| does open,v

the stack will immediately cool and open .the circuit between electrodes |82 and |83 of the hold tube |11 which causes complete deenergization of the resistor |18. If the motorvswitch 3| should stick in closed position cr the vmotor should otherwise fail to stop, the stack will'remain hot andconsequently the circuit through resistor |18 will not be broken at the electrodes |82 and |83. 1

Moreover, if the hold tube |11 should remain in its h ot position wherein electrodes |82 and |83 establish a circuit therebetween, such as may occur if the thermostatic element |81 should break or thefrlctional slip connection between the rod 8 3 and the member 88 should become inoperative, after either the limit control switch |18 or the room thermostat |55 are opened, then the ultimate safety resistor 18 will operate to open the lockout tube v22.

The continued flow of current through heating element |18 will cause the bimetalllc element |33 to warp and open lockout switch 22. Thus it will be Vnoted that the ultimate safety feature of the circuits shown will open the main line or power supply circuit should theapparatus fail to operate whereby complete protection against others may, by applying current knowledge,

readily' adapt the same for use under varying conditions of service, without eliminating certain features which may properly be said to constitute the essential items of novelty involved, Y

which items are intended to be dened and secured to me by the following claims.

I claims'v 1. Apparatus for a control system for oil burners or the like including fuel feeding means, actuating means therefor, and ignition means, said trolling said actuating means, a control circuit for controlling the operation of said switch, a transformer relay having a primary coil, a secondary coil in said control circuit, and a movable member influenced by the magnetic pull arising from the interaction of the' magnetic fluxes produced by current iiow through said` coils for actuating said switch into operative position, and means for reducing the load on said primary coil'to weaken the magnetic pull upon said movable member to holdthe same in actuated position but insuillcient upon release of said movable member upon current failure or reducs tion of currentito restore it to actuated position.

so. control apparatus comprising a switch for conaovaasa 2. Apparatus for a control system for oil burners or the like including fuel feeding means, ac-

tuating means therefor, and ignition means, said,

control apparatus comprising a switch for controlling said actuating means, a control circuit for controlling the operation of said switch, a transformer relay having a primary coil, a'lsecondary coil in said control circuit, and av movable member inuenced by the magnetic pull 1,0 arising from' the interaction of the magnetic iiuxes produced by the current flow through said coils for actuating said switch into operative position, means effective after initial operation of the burner for reducing the load on said primary coil and weakening the magnetic pull upon said movable member to hold the same in actuated position but insuflicient upon release of said movable member upon current failure or reduction of current to restore it to actuated position, and thermostatic means responsive to the temperatures produced by the burner` for controlling said control circuit.

- 3. Apparatus for a control system for oil burners or the like including fuel feeding means, actuating means therefor, and ignition means, said control apparatus comprising a switch for controlling said actuating means, a control circuit for controlling the operation of said switch, a transformer relay having a primary coil, a secondary coil in said control circuit, and a movable member influenced by the effective magnetic force produced by the inter-action of the magnetic fluxes resulting from current ilow through both coils for actuating said switch, a resistance element adapted to be inserted in said control circuit to reduce the load on said primary coil and to weaken the eiective magnetic force suiiciently to vhold said member in actuated position but insuflicient to vmove it to actuated position after release thereof upon current failure or reduction of current, a second switch for short-circuiting said resistance element until combustion is established at the burner, and thermostatic means adapted to respond to combustion conditions established by the burner for controlling the operation of said second switch.

4. Apparatus for a control system for oil burners or the like including fuel feeding means, actuating means therefor, and ignition means, said control apparatus comprising a switch for controlling said actuating means, a control circuit for controlling the operation of said switch, a transformer having a primary coil, a secondary coil in said control circuit, and a movable member influenced by the effective magnetic force resulting from the inter-action of the magnetic fluxes produced by current ow through the' primary and secondary coils for actuating said switch, and means for reducing the current flow through the secondary coil'to weaken the effective magnetic force suiciently to hold said mem- -ber actuated but insufficient to actuate said member after release thereof upon current failure or reduction of current, said means including a resistance element, a second switch for short-circuiting said resistance elementA until combustion is establishedv at the burner and a third switch for inserting said` resistance element in said control circuit when said second switch is opened. i

5. Apparatus -for a control system for oil burners or the like including fuel feeding means, actuating means therefor, and ignition means,

said control apparatus comprising a switch for controlling said actuating means, a control circuit 7 5 for controlling the operation of said switch, a

transformer having a primary coil, a secondary coil in said control circuit, a movable member influenced by the interaction of the magnetic uxes produced by current ow through said coils for actuating said switch, and means for reducing the load on said primary coil to weaken the effective magnetic flux whereby thesame will be only suicient tohold said member actuated, said means including a resistance in circuit with the secondary coil, a second switch for short circuiting said resistance until combustion is established at the burner, a third switch for inserting said resistance in said control circuit when said second switch is opened, and thermostatic means adapted to respond to combustion conditions established by the burner forx controlling ,the operation of said second and third switches.

6. Apparatus for a control system for oil burners or the like including fuelfeeding means, actuating means therefor, and ignition means, said control apparatus comprising a switch. for controlling said actuating means, a control circuit for controlling the operation of said switch, a transformer having a primary coil, a secondary coil in said control circuit, the interaction of the magnetic fluxes produced by the current ow through said coils serving to actuate said switch, and means for reducing the load on said primary coil to weaken the effective magnetic action upon said actuated switch but insufficient to eiect release thereof, said means including a resistance in circuit with the secondary coil, a second switch for short circuiting said resistance until combustion'is established at the burner, a third switch for inserting said resistance in said control circuit when said second switch is opened, and thermostatic means adapted to respond to combustion conditionsv established by the burner for controlling the operation of said second and third switches.

7. Apparatus for a control system for oil burners or the like including fuel feeding means, actuating means therefor, and ignition means,

Asaid control apparatus comprising a switch for controlling said actuating means, a control cir- 'cuit for controlling the operation of said switch,

a transformer having a primary coil, a secondary coil in said control circuit, means influenced by the temperatures produced by said burner for closing said control circuit, a movable member inuenced bythe inter-action of the magnetic flux produced by current ow through said coils for closing said swiitch, a resistance element adapted to be inserted in said control circuit to reduce the load on said primary coil after combustion is established at the burner, and means for inserting said resistance element including a recycling switch adapted to be opened upon Vestablishment of combustion and a hold switch adapted to be closed prior to the opening of said recycling switch and to remain closed to hold said resistance element in said control circuit during normal operation of said control apparatus.

` 8.A Apparatus for a control system for oil burners or the like including fuel feeding means, actuating means therefor, and ignition means, said control apparatus comprising a switch for controlling said actuating means, acontrol circuit for controlling the operation of said switch, a transformer relay having a primary coil, a secondary coil in said control circuit,'a movable armature influenced by the magnetic flux diverted through the armature when current ows through the secondary coil for closing said switch, a rei$tance element adapted to be inserted in said 10 controlling said actuating means, a. control circuit for controlling the operation of said switch, a transformer relay having a primary,` coil, a secondary coil in said control circuit, the interaction of the magnetic fluxes produced by the current flow through said coils serving to close said switch, a resistance element adapted to be inserted in said control circuit to reduce the load on said primary coil after combustion is established at the burner, and means for inserting said resistance element in said control circuit upon establishment of combustion.

10. Apparatus for` a control system for oil burners or the like, including fuel feeding means,

actuating means therefor, and ignition means,

said control apparatus comprising a switch for controlling said actuating means, a control circuit for controlling the operation of said switch, a transformer having a primary coil, a secondary coil in said control circuit, a movable member influenced by the inter-action of the magnetic fluxes produced by current flowV through said coils for closing said switch, aresistance element adapted to be inserted in said control circuit to reduce the load on said primary coil after combustion is established at the burner, means for inserting said resistance element in said control circuit including a recycling switch and a hold switch, means responsive to combusion conditions of the burner for controlling the operation of said recycling switch and said hold switch,

a thermal element influenced by the heat effects of the current flow through said control circuit upon failure of said combustion responsive means to actuate said recycling switch and said hold switch, and a switch ln the circuit of said primary coil controlled by said thermal element.

11. Apparatus for a control system for oil burners or the like including fuel feeding means,

actuating means therefor, and ignition means,

said control apparatus comprising a switch for controlling said actuating means, a control circuit, means comprising an electro-magnetic coil in the control circuit for controlling the operation of said switch, a resistor in said control circuit, thermal means influenced by the heat effects of the current flow through said resistor in the said control circuit for rendering the system inoperative until manual intervention, combustion responsive means to operatively deenergize said resistor, and a normally open auxiliary control circuit having therein a boiler limit control and said resistor, said limit control being operated by an abnormal boiler condition resulting from failure of said switch to open upon operative deenergization o1 the electro-magnetic coil to energize said auxiliary circuit for rendering said system inoperative.

12. Apparatus for a control system for oil burners or the like comprising fuel feeding means and actuating means therefor, said control apparatus comprising a switch for controlling the operation of said actuating means, a control circuit for controlling the operation of said switch, a transformer having its secondary coll in said 75 control circuit, said transformer including a movable armature adapted to be operated upon current flow through said secondary coil for actuating said switch, a resistance element adapted to be inserted in said control circuit to reduce the flow of current through said secondary coil sufficient to keep said armature in operated position but to prevent return of said armature to operated position after release thereof upon current failure or reduction of current, means for inserting said resistance element in said circuit, said means being responsive to the combustion conditions of the burner, and a second resistance element adapted tov be connected in series relation with said first resistance element and said secondary coil when said control circuit is opened whereby to reduce the current ow through said secondary coil sufficiently to release said amature and open said switch.

l`3. Apparatus for a control system for oil burners or the like comprising fuel feeding means and actuating means therefor, said control apparatus comprisinga switch for controlling the operation of said actuating means, a control circuit for controlling the operation of said switch, a transformer having its secondary coil in said control circuit, a movable armature adapted to be operated upon current flow through said secondary coil for actuating said switch, a resistance element adapted to be inserted in said control circuit to reduce the flow of current through said secondary coil sufllcient to keep said armature in operated position but to prevent return thereof to operative lposition when released therefrom upon current failure or reduction of current, means for inserting said resistance element in said circuit, said means being responsive to the combustion conditions of theburner, a second resistance element adapted to be connected in series relation with said first resistance and said secondary coil when said control circuit is opened whereby to reduce the our rent flow through said secondary coil suillciently to release said armature and open said switch, and a thermal device influenced by the heat effects of. the current flow through said second resistance element for opening the circuit through said switch upon failure of said armature to open said switch.

14. Apparatus for a control system for oil burners or the like, including fuel feeding means, actuating means therefor, said controlsystem comprising: a switch for controlling said actuating means, a control circuit, meansincluding a. reactor in the control circuit for controlling the operation of said switch, an electro-thermal cutoff for deenergizing said system, a normally open auxiliary control system having therein a boiler limit control and the resistor of said electrothermal cut-off, said limit control being operated by an abnormal boiler condition (resulting from failure of said switch to open upon operative deenergization of said reactor) to energize said auxiliary circuit for rendering said system inoperative.

15. In combination, fuel supply controlling means, actuating means therefor, a switch normally biased to one of its positions for controlling said actuating means, an electrical device for controlling said` switch and adapted to cause movement of said switch to its other circuit controlling position rvhen energized, an electrically operated time switch for terminating operation cf the system and including an operator which operates the time switch if the operator thereof is operatively energized for a predeter.

mined length of time, a main switch, circuit connections controlled by said main switch for energizing said device, a combustion responsive switch which opens upon cessation of combustion, a condition responsive switch which moves to a new circuit controlling position if said condition becomes abnormal by reason of failure of said actuating means switch to open upon deenergization of said device, and a circuit for said operator of said electrically operated time switch controlled by said combustion responsive switch and the condition responsive switch when moved to said new circuit controlling position and independent of said main switch.

Al5 16. In combination, fuel supply controlling means, actuating means therefor, a switch normally biased to open position for controlling said actuating means, electromagnetic means for controlling said switch to move the same to closed position against its bias, an electrically operated time switch for terminating operation of the system and including an operator which operates the time switch if the operator thereof is operatively energized for a predetermined length of time, a main switch, circuit connections controlled by said main switch for energizing the electromagnetic means in a manner to cause closure of the first-named switch, a combustion responsive switch which opens upon cessation of combustion, a boiler 'condition responsive switch which moves to a new circuit controlling position if said boiler condition becomes abnormal by reason of failure of said actuating' means switch to open upon deenergization of the electromagnetic means in such manner as to normally allow said first-named switch to open, and a circuit for said operator of said electrically operated time switch controlled by said combustion responsive switch and the boiler condition responsive switch 40 when moved to such new circuit controlling position and independent of said main switch.

17. In combination, fuel supply controlling means, actuating means therefor, a switch normally biased to one of its positions for controlling said actuating means, electromagnetic means for controlling said switch and adapted to cause movement of said switch to its other circuit controlling position when at least a portion thereof is energized, an electrically operated time switch for terminating operation of the system and including an operator which opens the time switch if said time switch operator is operatively energized for a predetermined length of time, a room thermostat, circuit connections controlled by said room thermostat for energizing at least a pore tion of said electromagnetic means, a combustion responsive switch which opens upon cessation of combustion, a condition responsive switch which closes if said condition becomes abnormal by reason of failure of said actuating means switch to move to its biased position upon deenergization of said portion of the electromagnetic means, and a circuit for said time switch operator independent of the room thermostat and controlled by said combustion responsive switch and condition responsive switch in series.

18. In combination, fuel supply controlling means, an actuator therefor, an actuator controlling switch normally biased to open position, an actuator controlling switch operator which causes closing of said actuator controlling switch against its bias when energized, an electro-thermal time switch for rendering the system inoperative and including a heating means, a main switch, combustion responsive switching means including a cold switch which opens upon the establishment of combustion and a hot switch which opens upon cessation of combustion, an initial energizing circuit for said actuating switch operator including said operator, main switch, cold switch and heating means in series, a maintaining circuit for said operator including said operator, main switch and hot switch in series, a switch which closes when a condition produced by the system becomes too high in value, and a circuit for the heating means controlled by said last named switch and said hot switch in series and independent of the main switch.

19. In combination, fuel supply controlling means, an actuator therefor, an actuator switch normally biased to open position, an electromagnetic coil in control of said actuator switch, an electro-thermal time switch for rendering the system inoperative and including a rst and a second heating element, a main switch, combustion responsive switching means including a cold switch which opens upon the establishment of combustion and a hot switch which opens upon cessation of combustion, a heater condition responsive switch which opens if the value of the heat condition to which it is responsive becomes too high, an initial energizing circuit for said electromagnetic coil including the main switch, a combustion responsive cold switch, said first heating element and said heater condition responsive switch in series, a maintaining circuit for said electromagnetic coil including the main switch, said heater condition responsive switch and combustion responsive hot switch in series, an energizing circuit for said second heating element controlled by the combustion responsive hot switch, and a shunt circuit for said second heating element controlled by the heater condition responsive switch and combus` tion responsive hot switch in series whereby the energizing circuit for said second heating element is completed only upon opening of said heater condition responsive switch while the combustion responsive hot switch is closed.

ALBERT L. JUDSON. 

